The invention relates to a power tool comprising a drive shaft for driving a tool, wherein on a free end of the drive shaft a support for securing a tool is provided.
Such a power tool is known from EP 0 369 390 A2.
The known power tool comprises an oscillatory drive by means of which a tool secured to the free end of the drive shaft is oscillated with high frequency between roughly 5000 to 25000 oscillations per minute at low pivot angle in the range between 0.5xc2x0 and 5xc2x0. Thus the tool can be oscillated about the longitudinal axis of the drive shaft to perform particular cutting tasks, for instance for cutting adhesive beads on windshield panes, if these have to be exchanged. In addition, there are various possibilities for applications in the field of cutting, sawing, grinding, polishing etc.
From EP 0 369 390 A2 it is known to provide the tool with a securement opening for form-fit securement onto a securement section of the drive shaft and for subsequent fixing by means of a nut that can be screwed onto the end of the drive shaft.
In addition, designs have become known by public use, wherein on a free end of the drive shaft a threaded bore is provided into which a securement screw can be screwed which rests with a screw head of sufficient diameter against the surface of the tool for securing same to the drive shaft.
To obtain a secure power transfer and to ensure a precise alignment of the tool with respect to the work location, a form-fit between the securement opening of the tool and the securement section of the drive shaft is desired.
A drawback in this design has been that a final fixation of the angular location of the tool with respect to the drive shaft can only be reached, when the respective securement nut or the securement screw, respectively, has been sufficiently tightened on the threads of the drive shaft. Only in a final moment, just before the final tightening of the nut or the screw, respectively, the tool will be secured against further rotation.
It is a first object of the invention to provide an improved power tool allowing a positive fit of a tool to a drive shaft of the power tool at an early time of the securement operation already, preferably already when positioning on the free end of the drive shaft.
It is a further object of the invention to disclose a power tool allowing a positive fit of a tool to a drive shaft of the power tool in various ways.
It is a further object of the invention to disclose an adapter for form-fit securement of a tool to a free end of a drive shaft of a power tool.
It is still a further object of the invention to disclose a drive shaft for a power tool suitable form form-fit securement of a tool by means of an adapter.
These and other objects of the invention are achieved by a power tool comprising a drive shaft for driving a tool, a recess at a free end of the drive shaft, a detachable securement flange having a securement section on a side facing the drive shaft, the securement section being form-fitted for insertion into the recess of the drive shaft and comprising a flange section on the opposite side, wherein the tool comprises a securement opening which is adapted to the shape of the securement section of the securement flange for form-fit securement of the securement opening of the tool to the securement section, when the latter protrudes from the outside to the securement opening into the recess of the drive shaft.
By contrast to a raised securement section at the free end of the drive shaft now a recess is provided on the free end of the drive shaft. All in all, the tool is form-fitted to the drive shaft by means of a securement flange which positively engages with the securement opening of the tool and which is form-fitted for insertion into the recess on the free end of the drive shaft. According to the invention, it is not necessary to tighten a screw or a nut first, until finally a form-fit, and thereby also a protection against angular rotation, is reached.
By contrast, the tool can be applied together with the securement flange onto the drive shaft and is immediately held form-fitted on the drive shaft by means of the securement flange, while thereafter a securing element, for instance a screw, is used to finally fix the tool in this position on the drive shaft.
To this end according to a preferred development of the invention a threaded hole for receiving a securement screw is provided on the drive shaft. The securement flange in this embodiment is penetrated by an opening for receiving the securement screw.
Thus the tool can initially be placed on the drive shaft together with the securement flange and can be form-fit secured, while thereafter the securement screw is introduced through the opening of the securement flange and is screwed into the threaded hole, to thus fix the tool to the drive shaft.
According to a further embodiment of the invention, the securement section of the securement flange comprises a uniform cross section for form-fit support in the recess of the drive shaft as well as for form-fit support in the securement opening.
Such a design is preferred when the form of the securement opening of the tool and the recess on the free end of the drive shaft are identical. In this case the securement section of the drive shaft having a uniform cross section can positively engage with the securement opening of the tool as well as with the securement opening at the free end of the drive shaft.
According to an alternative embodiment of the invention the securement section comprises a first region being adapted for form-fit support in the recess of the drive shaft, and further comprises a second region adapted for form-fit support in the securement opening, wherein the first and second regions are of different configuration.
Such a design is suitable, when the shape of the securement opening of the tool differs from the recess at the free end of the drive shaft and is not compatible therewith. In this case the two regions of the securement section of the securement flange can be adapted accordingly, to obtain a form-fit with the securement opening of the tool, as well as with the recess at the free end of the drive shaft.
In this case the securement flange simultaneously functions as an adapter between different shapes of the securement section of the tool on the one hand and the recess at the free end of the drive shaft on the other hand.
In a preferred development of the invention the securement flange comprises an enlargement for receiving a screw head at least partially recessed at the side facing away from the power tool.
In this way a securement screw which is utilized for securing the securement flange and the tool to the drive shaft, is received recessed or at least partially recessed on the securement flange, which allows an advantageous operation.
The recess at the free end of the drive shaft may be formed as a regular polygon, preferably as a hexagon.
In this case a continuous securement section on the securement flange together with a polygon shape matched thereto can be utilized for form-fit securement of the securement opening as well as of the recess to the free end of the drive shaft. Herein, the tool, such as known in the prior art, may comprise a securement opening in the shape of a dodecagon according to EP 0 369 390 A2, wherein between two adjacent outer corners always an inner corner displaced to the inside is formed, so that generally a star-shape results. Such a securement opening may for instance be form-fit secured by means of a continuous securement section in the shape of a hexagon, to the free end of the drive shaft.
According to an advantageous improvement of the invention in this design the corner regions of the polygonal recess at the free end of the drive shaft are enlarged to the outside by rounded sections.
Thereby a cramming of the securement section of the securement flange in the recess of the drive shaft is avoided. Also manufacture is simplified.
It will be understood that the recess of the drive shaft, the securement section of the securement flange and the securement opening of the tool can also be of any other desired shape, if the respective shapes are respectively adapted to each other.
Thus it is conceivable for instance to provide at the free end of the drive shaft a plurality of recesses at predetermined locations for receiving protrusions of the securement flange.
According to another embodiment of the invention the recess comprises a plurality of preferably six rounded tips which are located in regular angular intervals with respect to each other at a radial distance to the longitudinal axis of the drive shaft, wherein each pair of adjacent tips is connected by curved sections which bulge out from the adjacent tips into the direction of the longitudinal axis and coincide in a common summit.
Such a shape has particular advantages for obtaining a uniform torque transmission also at high load. Since there are no sharp-edged tips and since power transmission is obtained primarily by means of the curved sections between the rounded tips, punctual loads and high surface pressures are avoided, whereby a wear-out of the form-fit connection can be safely avoided, also after long usage.
Of course, if desired, also this shape may be combined with other shapes, if for instance the tool comprises a securement opening of different shape. Reversely, also a tool with a securement section of such a shape can be secured at the free end of the drive shaft by means of the securement flange, if the latter comprises suitably adapted regions at its securement section.
According to an alternative embodiment the object of the invention is achieved by a power tool comprising a drive shaft for driving a tool, an raised securement section at a free end of the drive shaft, a detachable securement flange having a securement opening on a side facing the drive shaft, the securement section being form-fitted for attachment onto the securement section, wherein the tool comprises a securement opening which is form-fitted to the shape of the securement section.
Also in this way the object of the invention is solved completely. This is a modification according to which on the drive shaft an embossed section is provided, whereon the tool can be supported with its securement opening form-fittedly, wherein the securement flange comprises a respective recess for form-fit engagement with the securement section of the drive shaft.
It will be understood that the above-mentioned and following features of the invention are not limited to the given combinations, but are applicable in other combinations or taken alone without departing from the scope of the invention.